count=0
'''
lb函数，输入n酒,t店,h花，无输出，找到一种count就+1
'''
def lb(n,t,h):
    global count
    if(n == 0):
        if(t == 0 and h == 0):
            count += 1
        return
    elif(n == 1 and h == n and t == 0):
        count += 1
        return
    elif(n < 0 or h < 0 or t < 0):
        return
    else:
        lb(n-1,t,h-1)
        lb(n*2,t-1,h)
n=int(input())
t=int(input())
h=int(input())
lb(n,t,h)
print(count)